How to make a "rope" like object with even width throughout the whole object? (image inside)
Probably the most common solution to this problem is to create a Bezier curve and use another Bezier curve (often a circle) as the Bevel Object (in the Bezier > Geometry properties).



https://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Bevelling_a_Curve has detailed documentation.

Your question is almost a duplicate of Make a 3D tube with a B&#233;zier curve? .